1. Field of Invention
This invention relates generally to medical procedures and in particular, minimally invasive medical procedures. One application of the present invention is in providing therapy to adjacent spinal vertebrae. More specifically, one application that uses the alignment jig is the facilitation of the reproducible deployment and placement of fixation device such as a screw, via an aligned, percutaneous access and approach, designed to relieve lower back pain and possibly improve disc health and prevent progression or transition of disease.
2. Problem Addressed
Some medical procedures require the application of a particular therapy in a particular place and inadvertent application of what was intended to be therapeutic intervention to a place within the body close to but different from the particular place can be undesirable. The need for precise placement of therapy is particularly important when working with the spinal column as is may be desirable to place a bone screw into adjacent bone segments to immobilize a portion of the spinal column but it would be undesirable to place the same screw into any other portion of the spine or spinal cord.
The application of therapy through minimally invasive procedures has many benefits for the patient but adds challenges to the surgeon seeking to deliver therapy to a specific location while working primarily outside of the body and accessing the site to receive therapy by limited access routes such as one or more percutaneous working cannula. The problem is made more difficult by the variations in patient anatomy as work on a particular patient in one specific portion of the particular patient's spinal column will not have the same exact dimensions and relationships between components in the spinal column as doing the same procedure on another patient.
The surgeon or other provider of medical therapy may rely on the general properties of human anatomy and on the benefits afforded by real-time imaging of the anatomy and any inserted instruments. For example, the surgeon may use one or more imaging devices to obtain fluoroscopic guidance to help maintain anterior/posterior and lateral alignment.
Turning to FIG. 1, the problem can be summarized as follows. A surgeon can locate the structures of interest in the patient's body 10 beneath the skin even in a minimally invasive procedure. With knowledge of anatomy and the desired therapy, the surgeon discerns the desired internal target path 20. The prior art has not provided a solution that allows the surgeon to translate the internal target path 20 to outside of the patient with adequate precision to allow the surgeon to confidently align the delivery of therapy (external alignment line 30) with the desired internal target path 20 plus whatever offset from co-linear 40 is desired. Sometimes it is useful to have some non-zero offset 40 from co-linear so that the delivery of therapy does not strike markers 50 inserted by the surgeon as part of the process of defining the internal target path 20.
Any tool or process to be used by a surgeon benefits from being easy to use even while gloved and wearing gloves that may be wet. A tool or process that requires a surgeon to use an assistant as the process cannot be completed with only two hands would be less desirable than a process that may be done with two or fewer hands. A tool or process that reduces the need for mental steps such as calculations and measurements, reduces possible sources of error for the process.